Docs builds on "a new test feature from Facebook" and the new Facebook platform outlined by Facebook at the f8 conference today. Cheng doesn't say a whole lot about that new Facebook feature, but does say it "allows us to build an instantly personalized and seamless document authorization & sharing experience directly from our site."

Cheng provided a few more details:

"Documents can be created directly within the app, or can be uploaded from your PC. After starting work on a document alone, you might then choose a few others with whom to share it. Or you might instead share it with all your friends, or you might share it with the world. Documents can be viewed and edited directly within a web browser – or, with a single click, you can edit them more richly and powerfully through the Microsoft Office software on your PC or Mac."

Office Web Apps is going to be available to different sets of customers in different ways, Microsoft officials have said.

Business users who want to run them inside a company on their own servers and/or via a Microsoft-hosted server will be required to pay some still-unknown subscription fee. Consumers who want to use Office Web Apps for free will be able to get an ad-supported version that they can access via Hotmail (the Wave 4 version) and/or Windows Live SkyDrive (also the Wave 4 version). Windows Live Wave 4 is slated to go to beta testers in the coming months and is expected to launch this summer.

I'm curious who out there might be interested in using this. I am not a document collaborator and never found Office Live Workspace -- which one might argue is the precursor to Docs.com -- to be useful. (Office Live Workspace is being supplanted by Office Web Apps, for what it's worth.)